The field of invention relates generally to micro-fabrication of structures. More particularly, the present invention is directed to patterning substrates in furtherance of the formation of structures.
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.
An exemplary micro-fabrication technique is shown in U.S. Pat. No. 6,334,960 to Willson et al. Willson et al. disclose a method of forming a relief image in a structure. The method includes providing a substrate having a transfer layer. The transfer layer is covered with a polymerizable fluid composition. An imprint device makes mechanical contact with the polymerizable fluid. The imprint device includes a relief structure formed from lands and grooves. The polymerizable fluid composition fills the relief structure, with the thickness of the polymerizable fluid in superimposition with the lands defining a residual thickness. The polymerizable fluid composition is then subjected to conditions to solidify and polymerize the same, forming a solidified polymeric material on the transfer layer that contains a relief structure complimentary to that of the imprint device. The imprint device is then separated from the solid polymeric material such that a replica of the relief structure in the imprint device is formed in the solidified polymeric material. The transfer layer and the solidified polymeric material are subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material such that a relief image is formed in the transfer layer. Thereafter, conventional etching processes may be employed to transfer the pattern of the relief structure into the substrate.
It is desired to minimize dimensional variations between the pattern recorded in the polymeric material from the pattern transferred into the substrate, referred to as transfer distortions. To that end, many attempts have been made to advance the micro-fabrication technique of Willson et al. For example, it has been desired to minimize the residual thickness of the solidified polymeric material. The thinner the residual thickness, the greater reduction in transfer distortions. The residual thickness of the solidified polymeric material is proportional to the residual thickness of the polymerizable fluid. However, the rate at which the polymerizable fluid fills the relief structure is inversely proportional to the cube of the residual thickness of polymerizable fluid. It is manifest that minimizing the transfer distortions increases the time required to record the pattern in the substrate. Thus, a tradeoff exists between throughput and minimization of transfer distortions.